Condensed Matter


Cause and Countermeasure of Crack Initiation in a 50Mw Steam Turbine Rotor

Authors: Yongsop Ri, Namhyok Ri, Jonggwang Pak, Iljin Kim, Zhihua Chen –Department of Mechanics Enineering, Kim Il Sung University, Pyongyang, DPR of Korea - School of Civil Engineering, Tianjin University, Tianjin 300072, PR of Chi

In this paper, the cause of crack initiation in 50Mw steam turbine rotors of “S” power station and a countermeasure for preventing it were studied. Many years ago, “S” power station restructured pipe paths to supply steam to turbines. The aim of the restructure was to save the heavy oil burning for startup. Since the restructure upto now, the turbines were started in a startup method different from standard. That is, the restructure made the current startup method different from the standard. Unfortunately, after having restructured them, cracks initiated in the rotors of the turbines in the case of starting in current startup method every certain period. The present study has been conducted to explain why the cracks initiated, and to establish a countermeasure for it. In the cases of starting the turbines in accordance with both the current and the standard startup methods, the change of convection heat transfer coefficients (CHTCs) and transient temperature and thermal stress were analyzed. Through these analyses, the cause of crack initiation in the case of current startup method was explained. And the low-cycle fatigue life until the cracks initiated was calculated and compared with experimental data. A new reasonable startup method was suggested as a countermeasure of a crack initiation. The new method not only could prevent crack initiation in the steam turbine rotors but also gave economic benefit. Keywords: steam turbine; thermal stress; low-cycle fatigue life; startup; rotor

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[v1] 2018-02-21 18:41:06

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